Advances in Copper and Nickel C‐N and C‐O Cross‐Couplings of (Hetero)Aryl Chlorides Enabled by Ancillary Ligand Development

The evolution of palladium‐catalyzed C‐N and C‐O cross‐coupling chemistry into first‐choice methods for the synthesis of aniline and phenol derivatives can be attributed to innovations in ancillary ligand design that facilitate challenging elementary steps of thermal catalysis. Inspired by this strategy, and in the quest to establish more sustainable thermal base metal catalysis that is competitive with and complementary to such precious metal protocols, several successful mechanism‐inspired ancillary ligand classes for use in enabling high‐performing copper and nickel catalysts have emerged over the last decade. In this Review we document key ancillary ligand advances of this type, with a focus on superlative copper and nickel catalysts that enable C‐N or C‐O cross‐couplings of cheap and abundant (hetero)aryl chloride electrophiles under operationally simple conditions of relevance to end‐users in academia and industry.